You said you were mixing 10-1, that is almost 10%. If it is actually less than that the effect will be lower. But mealworms are higher in protein and fat than most chicken feed, and also have a different ratio of things like calcium and Vitamin D3. So you are raising the protein, fat, and possibly some other nutrients, while lowering the calcium, vitamin D3, and likely many other nutrients. If you are giving any other treats in addition to mixing in the mealworms then their overall intake will be even more out of proportion to the amounts in a balanced chicken feed. Which is why it is frequently stated that total amounts of treats or other items fed in addition to their regular feed should be no more than 10%. And there is also the risky when mixing it with their feed that they will pick out and eat more of the “candy” (mealworms) and eat less of the pellets.
That’s just my opinion, but I have seen many other people say the same thing about mealworms and other treats. That they should never be mixed in with the regular food and only provided on an occasional basis.