Hi Hemant,
Running rlcdel will not affect your heuristic results as long as you have not deleted the forecast/requirements. Changing the master data fields multiple times also is not an issue if the master data values finally selected are OK.
If your master data for old products is same as for new ones (for which heuristics results are good) let that be like that.
Please make sure you have demand available, if needed create some more demand, also I assume have reassigned the products to the 000 model. You can also try running the SNP01 t-code with detailed log option selected, which may show you the error in your setup.
Regards,
Umesh