First be patient.It is nerve wracking.It takes time to get it all right and while you are ...check the temp Often!!!.
Unless you have a Brineas or a Genesis you will have these issue
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If it spiked for minutes it may not have hurt them as its takes them a while to warm up.
You do have to dinker with the temp .but every time you move the setting do it just a tiny bit and leave it for an hour or 2 so see where it takes you Then ajust more tiny bit at a time. You might try some washed rocks in the bator to sinc it so it wont cool fast on you anyway
Also sounds silly but mine did that at first ... then i put mine in.... my closet
.Read on here to do that ..but i thought I didnt have a draft problem but my closet settled the temp swings down a LOT
Unfortunately the better the bator is the more it costs.
HOWEVER if you are adventurous.. talk to Brookhaven she made one and i think you can do it for like$40 or $60 tops..Maybe less if you have some of the parts like an old computer its fan ...and an old cooler..
,You tube has videos on how to make them too.
Brook says hers is really reliable but you do need a temp gauge that ajusts the temp so it wont go too high . or low ..and a few other things. She is right though it does take awhile to know how your bator reacts and what to do