Florence,
While you can easily add another program to hit capitalization and punctuation, and there are many, many, many workbooks and programs for that out there, I think it is good to pause a moment for reflection and decide what is the cause of the problem.

From years of doing so many different grammar programs that it makes my head spin, I will tell you that Rod and Staff is hands-down the most thorough, systematic, God-honoring, all-inclusive English (grammar and writing) program out there. So, if this is true, then why are your kiddos struggling on the capitalization and punctuation portion?
So, here is the answer I've found through 20+ years of watching kiddos take standardized tests!

Using correct capitalization and punctuation is a habit that has to be formed. It is not something that cannot be taught and retained in a workbook format. It is something that has to be emphasized each and every day as children write.

To form the habit of using capitalization and punctuation correctly, make sure your kiddos are using these skills correctly in their own writing every day. I check everything my kiddos write every day! I use my pencil and editing marks to mark their writing and make them correct any needed capitalization and punctuation in everything they do.

If kiddos can do it in their own written work, they can do it on a test.
So, here are a couple of questions to ponder. How well do your kiddos do with the skills of capitalization and punctuation in their daily writing? Have you been requiring them to correct their written work daily if it isn't correct? If not, now is a great time to start.

I do all my corrections on my children's writing in pencil, underlining any letters needing to be capitalized three times, making an empty circle at the spot where punctuation is missing, and circling incorrectly spelled words and writing the correct spelling in the margin. My kiddos then erase and add the capital letters, erase and add the correct punctuation, and erase and copy the correct spelling (erasing my writing when they're done, so they have a clean copy).

With my little people, I have them correct their writing right as they are writing, or directly after they've finished. With my big people, I edit it and hand it back to be corrected later in the day.
Another thing to ponder is... Did your kiddos form incorrect habits of capitalization, spelling, and punctuation early in their writing years, prior to switching to HOD or Rod and Staff? If so, you can expect that it will take longer to undo a bad habit than it would normally take to form a good habit from the beginning.

I share this not to discourage you, but rather to encourage you to persevere. Habits take time to form!
One last thing that is great to know is that Rod and Staff covers so many of the skills tests in the language arts and reading sections of the subtests. So, if they did quite well in other areas, you should take a moment to feel good about that.

If spelling and capitalization have continued to be a weak area, then you know you need to work on forming correct habits there.

If it makes you feel better, you may want to make an index card for each capitalization and each punctuation rule taught in Rod and Staff. Then, you could number the cards and for awhile code the mistakes your kiddos make in their writing by number in the margin and have them read the corresponding rule card too when they correct their mistakes.

I wouldn't go overboard with this though, maybe just working one rule per week and adding to the rules as your kiddos get them down. Forming a habit will go further than the drill though.
Don't be discouraged!

Capitalization and punctuation were far away the lowest subtest scores for many students in every school I was at, not just in my classroom. So, it is a tough area for many kiddos! Often we had drilled the rules and practiced finding errors in passages daily in our classroom all year long, only to find that certain kiddos still did not perform well on the capitalization and punctuation portion of the standardized test. We discovered that very often these were the kiddos who habitually omitted these skills in their own daily writing, and then struggled in these same areas on the standardized test portions.

When I began having my whole classroom fix their mistakes each day, we found a much better end-of-the-year test result (but even more importantly, the kiddos written work improved too).
Blessings,
Carrie