What is the next course of action when some mutual funds in your SIP start showing losses?

Like i answered here SIPs are meant to be for long term investment. If the markets have fallen and your fund is also showing losses then it is not a sufficient reason to exit the fund. You may suffer from exit load unnecessarily.

If the fund is performing worse than its peers, then you should put the fund under watch. You might consider upping your investment int he fund in a corrected market, provided the fund is a good one. For best funds, you can check out jama.co.in and the Picks section.

Please see my answer here: What should I do if my mutual fund is under performing?