mixing different ink manufactures

I'm using Paul Roark's inksets. For those who aren't familiar with it, this set involves a six position cartridge inkset: one 100% carbon cart, four different dilution carts, and a blue/cyan toner to weaken the slight warmth of the carbon. The ink I used was from Inksupply.com. Mine is almost all gone, and that ink is no longer available from them. I have now an unused set of inks: carbon black, cyan, and blue from Inkjetcarts purchased in March of 2020 and now that source is no more.

Should I top off my Inksupply filled carts with the Inkjetcarts ink? Both sets use presumably the same carbon ink. The toner in the two sets are different however... Inksupply used a single color whereas InkjetCarts used two colors, blue and cyan. Is it good or bad practice to mix the two? Is my InketCarts carbon black expired?

If I top off the existing carts I won't have to buy new carts, I have two brand new sets, from the two companies manufactured. I can afford that, however. And I may have to buy fresh carbon ink, probably from OctoinkJet.

Thanks all!