I wouldn't add during lockdown. The new eggs have different requirements than the ones already incubating, which is why it isn't a good idea to stagger hatch.
I ad eggs to existing hatches all the time with no problem. I've read a lot against it but that was after I'd done it a bajillion times without having any problems and 90+% hatch rates.
I have eggs hatching in two weeks, and I'll keep you updated!!!! There's 10 Polish, 2 Seramas (My first ever!) four Silkies, and 6 Mille Fleur Cochins! It's a shared hatch, with three hens working together. Two of them have hatched together before, the other is a rescued frazzle (frizzlexfrizzle) who really wanted to hatch so I put her with my two Super Moms to make sure her eggs were covered, since she's all bald and everything...All three hens are Silkies, and this will be the fourth batch for one of them, she is an AWESOME mama!
Wow! You're busy over there! It sounds like you're going to have an amazing baby flock! Please do keep me posted
Here's my new baby! She's got 2 eggs to go. This one is with a Barred Rock daddy and a Buff Orph. She's all black with one little yellow spot on her head. I can't wait to see what she looks like.
Im in day 3 now of incubating. Ive got some blue laced red wyandottes that were mailed to me. Fingers crossed. Its a long shot but even if they dont hatch its a great learning opportunity for my kids and myself. Im confident in my incubating abilities but I feel like these poor eggies went through a lot on the trip here.