I've usually used cartridges to the very end, so not sure that's the issue. I'd wait a full 6 cycles at this dose before increasing. I also like to try a new cartridge before an increase.
By the way, I've found that Safeway pharmacy is the cheapest source for insulin and other diabetic supplies in B.C. Don't know if that's true in PEI, but I saved $15 the last time I bought insulin.