Off tasting home brew!!

So far i've brewed 6 batches total, and the first 2 turned out perfect. The last 4 have had an off taste like a really strong bitter taste. I use Chlorine 'Pink' solution to clean my equipment, and I use 'Iodophor' Iodine sanitizer. My question is could improper rinsing of the chlorine solution be causing the off taste? The first two batches the airlock was perking like crazy, but the last four batches not so much. Could temperature be playing a part because the first two batches were made in the summer, but the last four were made more towards the October and November. These are the only things I can thing of causing such a bitter taste. Any ideas would be great appreciated. Thanks

I think you will find that most all of us on this forum have switched to star-san for sanitization b/c it's just that good.No worries about off flavors and infection problems.Here's a link to help you diagnose off flavors.
The common Homebrew Off flavors and aromas in your beer along with the symptoms,causes and remedies.

Thanks alot..Cheers!