...straight compost, no blending with soil? might be too hot, not pH balanced,.... the OF soil is really not good, sorry to say mate,.. it's the [HASHTAG]#1[/HASHTAG] problem soil I see in here, just plain lousy shit; usually badly acidic, undercooked, full of garbage bits,... bug issue reported too,... Some get lucky with OK bags, other don't! Seedling isn't in there yet, so I'd say the reaction is to the compost itself,... this is usually a key component to good soils, but not the medium itself....
Get a good soil pH probe and save yourself a ton of beating,.. the Accurate 8 is good unit, I love mine--
hsoil: <---long probe here....
....transplanting is risky, difficult,....root damage will stunt them,... but that damn OF soil could be a time bomb frankly,.... Find different soil, Roots Organic original is fine, readily available,... Kings Mix; Sanctuary Soil brand is nice too....