When בה''ב Falls out on Pesach Sheini

This calendar year when Erev Pesach is on shabbos will also have the rare occurrence the second Monday of selichos  behab fall out on Pesach Sheini 14th day of Iyar. Since many have the minhag not to say tachnun on the day of pesach sheini the poskim discuss what to do about those who fast on behab as well as saying selichos.  Rabbonei yerushalayim would not fast or say selichbos and avinu malkeinu. some recite an abridged version of selichos while others say all of it (Luach Eretz Yisroel). The siddur yaavetz says that it is permitted to fast and you say selichos. The chazon Ish would say tachnun and למנצח on pesach sheini since it is not brought down in the shulchan aruch among the days that you do not recite tachnun and according to him selichos behab is said too. 

In Lakewood, the minhag hayeshiva is to say the selichos but to stop after "הרחמים והסליחות" which is after the viduy (just as would be done if there is a bris). Tachnun and avinu malkeinu are not said. However on mincha erev pesach sheini  minhag  hayeshiva in Lakewood is to say tachnun  since the simcha on pesach Sheni was only during the time that the Korban was brought and not all day or the night before which than you wont say tachnun at the mincha that preceeds it (Noheg Bachachma)

The Selichos of Behab:

In the beginning of the months of Cheshvan and Iyar, many communities have a custom to recite selichos on Monday, Thursday and Monday. This is the why these selichos are referred to as BeHaB – which is an acronym for Beis (Monday), Hey (Thursday) and Beis (Monday). The reason why selichos are recited at the beginning of those two months is in order to atone for any sins that were committed due to the excesses of the recently celebrated Yom Tov (Shulchan Aruch 492 and Mishnah Berurah ad loc.).

During a year when Erev Pesach occurs on Shabbos, as it did this year 5785, the second Monday of selichos in Iyar falls out on Pesach Sheini. In this case, many are accustomed to skip selichos altogether on this day, while some recite an abridged version (Luach Eretz Yisroel).