I've seen mistakes done by my seniors and although I've never corrected them, I wonder if I should. I'm afraid they'd feel humiliated. They are probably 5th or 6th kyu(it starts at 6 here) and I don't even have my gi yet. So is it proper to correct your seniors?
If you really have a question about your
technique, there is nothing wrong with bowing to the sensei and asking for his/her help. If you have a question about your partner's
technique try your best to give them good honest ukemi as it's taught in the dojo. Also please realize that although you're partners might be making mistakes, they might be aware of those mistakes and that they might actually be working on them. There is a reason they are 6th and 5th kyus -- their techniques are not going to be perfect yet. It's like telling an overweight/ obese person they are "fat". You don't have to tell them that -- they already know it. If all you want to do is point out their mistakes, and since you only have three days experience then I don't see how you will help them -- aikido-wise
-- other than pointing out their errors. I assure you, you have errors, too.
Also, you might have awareness of openings and how you might be able to counter from your previous martial arts background. Just be patient and take the time to learn aikido, and your previous MA background will be obvious to others as you train, and you will eventually be able to share that with them.