I have 6 or so cukes planted this year (straight eight heirloom from burpee) and they're producing like crazy! The first few that I picked were great, and the kids LOVE cucumber. This morning I picked 4 more, and just went to cut them up for lunch and all but ONE were REALLY bitter and tasted awful. Is this a product of too much heat? Did I pick them too late (the were kinda fat/round)? Help!!